1. Field of the Invention
The present invention is generally concerned with lubricant dispersants. More particularly, it is concerned with additives, and their use in lubricants as dispersants, of a product containing a hydroxyaromatic-substituted maleic anhydride moiety.
2. Discussion of the Prior Art
It is known that in the normal use of organic industrial fluids such as lubricating oils, transmission fluids, bearing lubricants, power transmitting fluids, and the like, the base medium is subjected to oxidizing conditions which can result in the formation of such things as sludge, lacquers and corrosive acids. These are undesirable at the least and can, under certain conditions, set up destructive forces not only toward the lubricant, but also toward the part being lubricated. That is to say, these oxidation residues or heavy contaminants may interfere with the normal operation of the fluid, increase its viscosity and even cause severe damage to the equipment itself.
In the lubrication of modern engines, it is particularly important that the oil composition be able to prevent acids, sludge and other solid contaminants from collecting at the point of contact of the moving parts. For example, poor piston travel and excessive engine bearing corrosion may result unless the oil can prevent oxidation products from depositing on the inner surfaces thereof.
One way of decreasing these difficulties is to add to the base organic fluid a detergent or dispersant additive that is capable of dispersing the solid particles to prevent them from interfering with the normal operation of any equipment being lubricated, leaving the lubricated surfaces relatively clean. The present invention is believed to solve the problem of dispersing solid contaminants with products that are not suggested by any prior art.
Metal-free nitrogen-containing dispersants are known in the art. For example, U.S. Pat. No. 3,445,386 discloses lubricant compositions containing polypropenylsuccinimide, -amides, -imidozolines and -imidozolidines, where the polypropenyl group is derived from polypropene having a number average molecular weight of from 500 - 3000. Exemplary of the compounds disclosed is: ##STR1##